1. Field of the Invention
The present invention relates to gas lasers, and more particularly, to improved means for providing ultraviolet preionization for pulsed gas lasers.
2. Description of the Prior Art
It is known that the discharge stability of pulsed gas lasers is greatly enhanced by supplying a preionizing radiation to the gaseous medium. Previous preionization sources have used: (1) spark boards which produce an array of arcs leading to ultraviolet radiation, (2) corona discharges embedded in the cathode, (3) corona discharges between metallic blades, (4) discharges to auxiliary wire electrodes, and (5) surface discharges. These methods have involved cumbersome geometries not amendable to small laser volumes having output cross-sectional areas of about 25 square millimeters or less, for example.
In the Review of Scientific Instruments, 50 (12), Dec. 1979, page 1542, V. Hasson et al use a preionizer comprising a first wide flat copper foil inside a thin insulating board placed lengthwise opposite the lateral opening between the two main laser electrodes, and a second foil strip on the outside of the board. The foils are connected respectively to the same high voltage terminals as the two laser electrodes.
In the Review of Scientific Instruments, 51 (2), Feb. 1980, page 216, N. Menyuk et al mention a UV-preionization system which consists of a row of series-connected spark gaps.